The paper presents a theoretical analysis of the time variation of strain gradients in a tensile specimen of rate-dependent material, the analysis being based on the assumption that the strain rate in the material is a function of the local values of stress and strain. The theory is used to determine the criterion for the growth of t'tr~in rrmdients, and it is shown that for a given material there exists a region of the strpss-str•ain plane in which these g-radients increase indefinitely with

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... me. The theory is applied to materials with specific types of rate-dependence, and the results are related to experimental data obtained at constant rates nf strain. On leave from Department of Engineering Science, Universitv of Oxford.